Hot-Cathode Tube Calibration Service
A BA-1/C tube and control calibrated by the National Institute of Standards and Technology (NIST), Gaithersburg, MD is used as a standard.
The tube under test is attached to the test stand opposite the NIST tube. A GFV IGC-1 is used as calibrate control; the control's grid bias is set to 180 ±1 V; filament bias is verified as 30 ±1 V; emission current is set to 1 ±0.01 mA. These values are maintained over the measurement cycle. The calibrate control is set for a tube gauge factor of 10.0/Torr.
The system is pumped until the background pressure indication from the NIST system indicates 2x10-6 Torr or below. When the background pressures stabilize they are recorded as Ptbg for the test equipment and Pnbg for the NIST equipment. The leak is then gradually opened until the NIST equipment reads 5 ±2 x10-5 Torr. The readings from the two controls are recorded as Pt for the test equipment and Pn for the NIST equipment.
The value of gauge factor G for the test tube is then calculated as
G = 10.0 x (Pt - Ptbg)/Pn - Pnbg).
If the tube under test has two filaments, the procedure is repeated for the second filament.
Order CERT/N where N is the number of tube filaments to be calibrated. Price is $150.00 for each filament to be calibrated.